Twin Tropical Storms Goni and Atsani Strengthen in Western Pacific; Strong Winds Lashing Saipan

Jon Erdman
Published: August 15,2015

Just one week after Typhoon Soudelor raked Saipan, Taiwan, Japan's Ryukyu Islands and southeast China, the tropical western Pacific is recharging with a pair of tropical storms, likely to become twin typhoons in the days ahead. Even as cleanup efforts continue, Saipan is once again taking the brunt of a tropical storm.
(SOUDELOR RECAPS: Impacts | Reports | Images | Rain Visualization)

Infrared Satellite: Twin Systems

Both systems have now become named tropical storms, Goni and Atsani. Goni's center tracked very close to Guam and the Northern Mariana Islands, including Saipan. Meanwhile, Atsani is churning several hundred miles to the east.
(FLASHBACK: Six Tropical Cyclones At Once)
With low wind shear, a moist atmosphere and ample ocean heat content, each of these tropical storms is expected to further intensify into a typhoon in the coming days.

Saipan and Guam: Tropical Storm Warning

The most immediate concern is with Tropical Storm Goni, which has been affecting Guam and the Northern Mariana Islands.
The National Weather Service has issued a typhoon watch for Saipan and Tinian, meaning typhoon-force winds of 74 mph or greater are possible, although the strongest winds have now passed by to the west.

Guam/Marianas Radar and Wind Reports

A girl helps her parents repair their storm-damaged home by removing nails from plywood on Saturday, Aug. 8, 2015, in Saipan, Northern Mariana Islands.
(AP Photo/Daniel Lin)

A tropical storm warning remains in effect for those islands as well as Guam and Rota. Tropical storm-force winds (39 mph or greater) have occurred as the center passed through the islands. Off Saipan, a sustained tropical storm-force wind of 43 mph was reported just before 11 p.m. local time (7 a.m. EDT) Saturday. A peak gust of 61 mph was recorded there at 10:23 p.m.
On Guam, Andersen Air Force Base clocked a 49-mph sustained wind at just before 5 a.m. local time Sunday (3 p.m. EDT Saturday), with gusts to 58 mph, as a heavy rain band lashed the northern end of Guam. Guam's capital, Hagatna, has gusted as high as 46 mph as of this writing.
According to the National Weather Service in Guam, the center of Tropical Storm Goni was located 75 miles northwest of Rota, 90 miles west of Saipan, and 105 miles north-northwest of Guam, as of 2 p.m. local time Sunday.
The Joint Typhoon Warning Center says maximum sustained winds have increased to 65 mph. The Japan Meteorological Agency, whose figures are usually more conservative than those of JTWC, has raised Goni's maximum winds to 60 knots, or 69 mph.
The turn of events couldn't be worse news for Saipan, still struggling to recover from Typhoon Soudelor.
The Pacific News Center reported about 4,000 households in Saipan, or over 25 percent, have requested assistance from the Federal Emergency Management Agency.
Power outages and a lack of running water and food have plagued the 44-square-mile island about 135 miles northeast of Guam since an intensifying Soudelor hit the island square on Aug. 2.
(WATCH: Saipan Struggles After Soudelor)
Guam's main newspaper, the Pacific Daily News, says some families on Guam are also recovering from typhoon damage – in their case, damage from Typhoon Dolphin back in May. Dolphin's eyewall passed over Guam, delivering gusts as high as 106 mph to the northern end of the island.
Tropical Storm Goni is forecast to continue to strengthen as it passes by the Marianas this weekend. Unfortunately, like Soudelor, this new system may begin to undergo a period of rapid intensification before it can clear that island chain.
As a result, bands of locally heavy rain are expected to continue Sunday and possibly Monday for Guam and the Northern Marianas. Even heavier rain arrived Saturday and continues Sunday, prompting flash flood warnings for Guam and Rota.
Guam International Airport reported a 31-hour rainfall total of 12.58 inches through 1 p.m. local time Sunday. Andersen Air Force Base picked up 11.36 inches of rain in the same time period. (Guam is 14 hours ahead of U.S. Eastern Daylight Time.)
This system may not completely clear the islands until Monday, but the faster-than-expected forward motion this weekend may get Goni out of the region a little faster than previously thought.
Strong and potentially damaging winds have occurred on Saipan and Tinian. The island of Rota likely also experienced strong winds as Goni crosses through the island chain.
(FORECAST: Guam | Saipan)

Two Threats to Asia Ahead?

Once Goni departs the Marianas, rapid intensification is possible, with the system possibly attaining super typhoon status (sustained winds at least 150 mph) at some point next week, though recent forecasts have tempered that outlook a bit.

Forecast Path: Goni

Twin Typhoons Outlook

Steered by high pressure aloft just south of mainland Japan, Goni may eventually pose a threat as a strong typhoon anywhere from the northern Philippines to Taiwan or Japan's Ryukyu Islands, including Okinawa, late next week.
(FORECASTS: Taipei | Shanghai)
Parts of eastern China and the Korean Peninsula may be threatened early the following week.
But that's just the first system. What about its twin to the east, Tropical Storm Atsani?
While it's much too far out in time to be certain, current indications suggest the eastern system, instead of following in the wake of the first system, may instead track more toward the northwest next week.
This may occur thanks to a weakening upper-level high to its north, shifting instead to its east.
This would be well northeast of Saipan and Guam, if it holds true.
However, Atsani may eventually pose a threat to mainland Japan late next weekend or early in the following week, if the jet stream doesn't curve it into the open waters of the north Pacific Ocean in time.
(FORECAST: Tokyo | Osaka)
Again, this is more than seven days out, and the forecast can and likely will change.
(MORE: Expert Analysis | Hurricane Central)
Interests in the western Pacific, including Guam, Saipan, Taiwan, Japan, the northern Philippines and eastern China should monitor closely the progress of each of these systems.
Including Halola migrating westward from the central Pacific basin, there have already been 14 named storms so far this year in the Northwest Pacific basin. Ten of those became typhoons -- equivalent to hurricanes -- and five of those (Maysak, Noul, Dolphin, Nangka and Soudelor) became "super typhoons", packing sustained winds estimated of at least 150 mph.
According to Colorado State University scientist, Dr. Phil Klotzbach, the Northwest Pacific basin had seen record levels of year-to-date tropical cyclone activity through early August, as measured by the accumulated cyclone energy or ACE index.
Senior meteorologist Nick Wiltgen contributed to this report.

MORE: Typhoon Soudelor Photos